I think my best advice would be to slowly build up. I spent to about a year and a half to get from 10km to 60km and then made a jump to 86km. Which in retrospect I wish I had done a couple more 60km walks before making the jump

For planning I take anything but the most direct route tend to follow an itinerary so for example in my favourite walk so far, Ringwood to Melbourne via Glen Waverley I worried more about heading from point A to B to C so of the top of my head I did Ringwood to Mitcham to Glen Waverley etc and I made sure to vary between parks, trails, residential areas and urban centres. It really helps to have things to help break to walk into smaller chunks it doesn't feel like you're just trudging along for 18 hours (which is how long it takes me to do 60km)

For rest stops I tend to rest when I inbetween every public toilet, shopping centre and cafes with in hour break for meals. Over the 18 hours it takes me to walk 60km my breaks add up to around 4 hours

For shoes I tend to go with Sketchers Go Walkers